Strain characteristics and antibiotic susceptibility of isolates of Neisseria gonorrhoeae causing disseminated gonococcal infection in Australia. Members of the Australian Gonococcal Surveillance Programme

Dinner date: Neisseria gonorrhoeae central carbon metabolism and pathogenesis

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhea, is a human-adapted pathogen that does not productively infect other organisms. The ongoing relationship between N. gonorrhoeae and the human host is facilitated by the exchange of nutrient resources that allow for N. gonorrhoeae growth in the human genital tract. What N. gonorrhoeae 'eats' and the pathways used to consume these nutrients have been a topic of investigation over the last 50 years. More recent investigations are uncovering the impact of N. gonorrhoeae metabolism on infection and inflammatory responses, the environmental influences driving N. gonorrhoeae metabolism, and the metabolic adaptations enabling antimicrobial resistance. This mini-review is an introduction to the field of N. gonorrhoeae central carbon metabolism in the context of pathogenesis. It summarizes the foundational work used to characterize N. gonorrhoeae central metabolic pathways and the effects of these pathways on disease outcomes, and highlights some of the most recent advances and themes under current investigation. This review ends with a brief description of the current outlook and technologies under development to increase understanding of how the pathogenic potential of N. gonorrhoeae is enabled by metabolic adaptation.

Molecular characterisation of Neisseria gonorrhoeae associated with disseminated gonococcal infections in Queensland, Australia: a retrospective surveillance study

OBJECTIVES

Gonorrhoea caused by Neisseria gonorrhoeae is the second most notified sexually transmitted infection (STI) in Australia and the case numbers for this STI have been increasing globally. Progressive gonococcal infection may lead to disseminated gonococcal infection (DGI), which causes significant morbidity among patients. This study aims to examine the genetic diversity of N. gonorrhoeae isolates collected in Queensland from January 2010 to August 2015 and to determine factors associated with DGI in Queensland.

DESIGN

Retrospective surveillance study for epidemiological purposes.

SETTING

All gonorrhoeae isolates referred by private and public pathology laboratories to the state of Queensland, Australia Neisseria reference laboratory.

METHODS

Between January 2010 and August 2015, 3953 N. gonorrhoeae isolates from both metropolitan and regional Queensland infections were typed with NG-MAST (N. gonorrhoeae multiantigen sequence typing) to assess the genetic diversity between strains. Whole-genome sequencing (WGS) was used to investigate strain-related factors associated with DGI.

RESULTS

ST6876 was the most common NG-MAST type, detected in 7.6% of the isolates. DGI was significantly more likely in females <30 years (OR 13.02, p<0.0001) and in older males >30 years (OR 6.04, p<0.0001), with most cases originating from North Queensland (OR 8.5, p<0.0001). Strains harbouring PIA class of porB type were associated with DGI (OR 33.23, p<0.0001).

CONCLUSION

Genotyping techniques, such as NG-MAST and WGS, are proving instrumental in providing an insight into the population structure of N. gonorrhoeae, and genetic mechanisms of pathogenesis, such as for DGI.

Gonococcal arthritis: case series of 58 hospital cases

OBJECTIVES

Extra-genital manifestations of gonococcal infection are rare (0.5-3%). Among them, gonococcal arthritis (GA) is the most frequent, accounting for 30-90% of disseminated infections. Our study aimed to describe all hospital cases of GA in Reunion Island, a French overseas territory.

METHODS

We conducted a retrospective, multicentric, observational study of all cases of certain, probable or possible GA from 2008 to 2020.

RESULTS

We identified 58 cases of GA, mostly certain cases (n = 48). Sex ratio was balanced, but men were older than women (51 vs 27 years, p < 0.001). A total of 41% had travelled abroad during the previous 3 months, mostly in Madagascar or South-East Asia. The most frequently infected joint was the knee, followed by ankle, wrist and fingers or carpal joints. Only 16% of cases had genital symptoms, but 50% had another extra-genital manifestation, mainly skin lesions (40%). Positivity rate of joint puncture was 91%, with a purulent liquid. Only 58% had a positive culture, and 33% had only a positive PCR. There was no 3GC-resistant strain. In comparison with gonococcal infection without arthritis, patients were older and had fewer genital but more extra-genital symptoms. On discharge 60% had persistent articular symptoms. GA represented 18% of all hospitalised septic arthritis cases with microbial identification in 2019.

CONCLUSIONS

GA is rare but it is important to make an early diagnosis and treat promptly, as joint destruction may be important, leading to persistent symptoms after discharge. PCR use in joint puncture is useful in cases with negative culture.

Case Report: Severe Disseminated Gonococcal Infection with Polyarticular Gout: Two Cases in Older Travelers

Two male travelers with histories of gout and hazardous alcohol consumption, presented with a triad of severe culture-positive disseminated gonococcal infection, crystal-positive polyarticular gout, and gonococcal soft tissue collections, following unprotected sexual contact in The Philippines. Both men initially attributed symptoms to gout, since their usual joints were affected, but clinical deterioration occurred with self-administration of anti-inflammatory agents alone. The clinical courses were severe and protracted, requiring aggressive management of infection with prolonged intravenous antimicrobials and repeated surgery, and prolonged anti-inflammatory agents for gout. Joint symptom onset in each case occurred within a week of sexual exposure in conjunction with hazardous alcohol ingestion. We speculate that acute dissemination of infection to previously damaged joints triggered polyarticular gout, with progressive infection, exacerbated by unopposed anti-inflammatory agents and delayed antibiotics. Disseminated gonococcal infection can occur with polyarticular gout and delays in recognition and treatment, including while traveling, can lead to severe disease from both.

Neutral sphingomyelinase 2 is a key factor for PorB-dependent invasion of Neisseria gonorrhoeae

Disseminated gonococcal infection (DGI) is a rare but serious complication caused by the spread of Neisseria gonorrhoeae in the human host. Gonococci associated with DGI mainly express the outer membrane protein PorBIA that binds to the scavenger receptor expressed on endothelial cells (SREC-I) and mediates bacterial uptake. We recently demonstrated that this interaction relies on intact membrane rafts that acquire SREC-I upon attachment of gonococci and initiates the signalling cascade that finally leads to the uptake of gonococci in epithelial cells. In this study, we analysed the role of sphingomyelinases and their breakdown product ceramide. Gonococcal infection induced increased levels of ceramide that was enriched at bacterial attachment sites. Interestingly, neutral but not acid sphingomyelinase was mandatory for PorBIA -mediated invasion into host cells. Neutral sphingomyelinase was required to recruit the PI3 kinase to caveolin and thereby activates the PI3 kinase-dependent downstream signalling leading to bacterial uptake. Thus, this study elucidates the initial signalling processes of bacterial invasion during DGI and demonstrates a novel role for neutral sphingomyelinase in the course of bacterial infections.

Innate recognition by neutrophil granulocytes differs between Neisseria gonorrhoeae strains causing local or disseminating infections

Members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family serve as cellular receptors for Neisseria gonorrhoeae. More specifically, neisserial colony opacity (OpaCEA)) proteins bind to epithelial CEACAMs (CEACAM1, CEA, CEACAM6) to promote bacterial colonization of the mucosa. In contrast, recognition by CEACAM3, expressed by human granulocytes, results in uptake and destruction of Opa(CEA)-expressing bacteria. Therefore, CEACAM3-mediated uptake might limit the spread of gonococci. However, some strains can cause disseminating gonococcal infections (DGIs), and it is currently unknown how these strains escape detection by granulocyte CEACAM3. Therefore, the opa gene loci from N. gonorrhoeae strain VP1, which was derived from a patient with disseminated gonococcal disease, were cloned and constitutively expressed in Escherichia coli. Similar to Opa proteins of the nondisseminating strain MS11, the majority of Opa proteins from strain VP1 bound epithelial CEACAMs and promoted CEACAM-initiated responses by epithelial cells. In sharp contrast to the Opa proteins of strain MS11, the Opa proteins of strain VP1 failed to interact with the human granulocyte receptor CEACAM3. Accordingly, bacteria expressing VP1 Opa proteins were not taken up by primary human granulocytes and did not trigger a strong oxidative burst. Analysis of Opa variants from four additional clinical DGI isolates again demonstrated a lack of CEACAM3 binding. In summary, our results reveal that particular N. gonorrhoeae strains express an Opa protein repertoire allowing engagement of epithelial CEACAMs for successful mucosal colonization, while avoiding recognition and elimination via CEACAM3-mediated phagocytosis. A failure of CEACAM3-mediated innate immune detection might be linked to the ability of gonococci to cause disseminated infections.

Disseminated gonococcal infection presenting as vasculitis: a case report

A 50-year-old man with alcoholic liver disease presented with fever, tenosynovitis, polyarthritis and a vasculitic rash on the hands and feet for 4 days. He had neutrophilia and raised inflammatory markers. He had no history of sore throat, urethral discharge or travel abroad. His initial blood cultures were negative, and he was treated for vasculitis with steroids. The rash and arthritis seemed to improve initially, but he had another episode of fever. Repeat blood cultures grew Neisseria gonorrhoeae,and he received intravenous ceftriaxone followed by oral ciprofloxacin. He had marked improvement in rash, tenosynovitis and arthritis, and the fever dropped. He also had chlamydial urethritis and received azithromycin. The presentation of disseminated gonococcal infection after a presumptive episode of asymptomatic urethral gonorrhoea is highlighted.

Strain-specific differences in Neisseria gonorrhoeae associated with the phase variable gene repertoire

Background

There are several differences associated with the behaviour of the four main experimental Neisseria gonorrhoeae strains, FA1090, FA19, MS11, and F62. Although there is data concerning the gene complements of these strains, the reasons for the behavioural differences are currently unknown. Phase variation is a mechanism that occurs commonly within the Neisseria spp. and leads to switching of genes ON and OFF. This mechanism may provide a means for strains to express different combinations of genes, and differences in the strain-specific repertoire of phase variable genes may underlie the strain differences.

Results

By genome comparison of the four publicly available neisserial genomes a revised list of 64 genes was created that have the potential to be phase variable in N. gonorrhoeae, excluding the opa and pilC genes. Amplification and sequencing of the repeat-containing regions of these genes allowed determination of the presence of the potentially unstable repeats and the ON/OFF expression state of these genes. 35 of the 64 genes show differences in the composition or length of the repeats, of which 28 are likely to be associated with phase variation. Two genes were expressed differentially between strains causing disseminated infection and uncomplicated gonorrhoea. Further study of one of these in a range of clinical isolates showed this association to be due to sample size and is not maintained in a larger sample.

Conclusion

The results provide us with more evidence as to which genes identified through comparative genomics are indeed phase variable. The study indicates that there are large differences between these four N. gonorrhoeae strains in terms of gene expression during in vitro growth. It does not, however, identify any clear patterns by which previously reported behavioural differences can be correlated with the phase variable gene repertoire.

An unusual cause of an epidural abscess

A previously well 30-year-old man presented with severe progressive back pain, joint pain and fever. Magnetic resonance imaging confirmed an epidural abscess. A sexual history revealed both risk factors for and previous symptoms of a sexually acquired infection. Neisseria gonorrhoeae was isolated from a rectal swab and from a wrist aspirate, consistent with disseminated gonococcal infection. The epidural abscess resolved clinically and radiologically after treatment for N. gonorrhoeae with ceftriaxone.

Sexually transmitted infections, adverse pregnancy outcome and neonatal infection

Prevention and treatment of sexually transmitted infections (STIs) in the sexually active population are the main steps to prevent perinatal infection. However, the spread of STIs continues at an astronomical pace despite various attempts at controlling the epidemic. An important reason for this lack of STI control is that a large percentage of infected people go untreated because they have asymptomatic or unrecognized infections. The microbial differential diagnosis of STIs implicated in adverse pregnancy outcome is broad and includes viral, bacterial and protozoal infections. Infertility, ectopic pregnancy, pelvic inflammatory disease, chorioamnionitis, premature rupture of membranes, preterm birth and puerperal sepsis are some of complications seen in women as a result of infection with sexually transmitted pathogens. In addition, STIs may facilitate the acquisition and transmission of HIV. In the fetus or neonate, complications include abnormalities of the major organ systems. Infections in the form of pneumonia or conjunctivitis may also occur. Due to the lack of simple, inexpensive and sensitive point-of-care tests, screening for STIs in pregnancy is not performed routinely.

Experimental transmission of Neisseria gonorrhoeae from pregnant rat to fetus

Sprague-Dawley rats were infected on day 20 of pregnancy by intraperitoneal inoculation with Neisseria gonorrhoeae. Disseminated gonococcal infection (DGI) and pelvic inflammatory disease (PID) strains in the presence of C1q but not in the presence of bovine serum albumin (BSA) were able to spread from the pregnant rat to the fetus and resulted in fetal mortality. Transmission of DGI and PID strains that are serum resistant (ser(r)) and sac-4 positive but not of a local infection strain that is ser(s) and sac-4 negative was facilitated by the C1q-dependent mechanism. This study provides the first experimental model that may mimic the transmission of gonococcal infection from mother to the fetus during pregnancy.

The frequency of co-infection with Neisseria gonorrhoeae and Chlamydia trachomatis in men and women in eastern Sydney

The frequency of simultaneous infection with Neisseria gonorrhoeae and Chlamydia trachomatis in men and women in Eastern Sydney was examined prospectively over a 21 month period in patients from whom appropriate specimens were obtained. In men gonococcal disease (113 cases) and chlamydial infections (124 cases) occurred in approximately equal frequencies, but there were only 4 instances (3.5%) where C. trachomatis was detected at the same time as N. gonorrhoeae. Demographic data and phenotypic profiles of the gonococci isolated suggested that much of the gonorrhea occurred in homosexual men who are generally considered to have a low incidence of chlamydial disease. Gonococcal disease (34 cases) was far less common than chlamydial infection (112 cases) in women, but co-infection with chlamydia was noted in 6 (17.6%) of the cases of gonorrhea (p < 0.01). The current recommendation for the routine addition of tetracyclines to gonococcal treatment regimens for men requires revision.

A case cluster of possible tissue invasive gonorrhoea

OBJECTIVE

To describe a cluster of patients presenting with severe symptoms and infected with an unusual strain of Neisseria gonorrhoeae.

SETTING

A north London Department of Sexual Health.

PATIENTS

Five patients were linked by reported sexual contact or other epidemiological evidence as part of a cluster of gonococcal infection. Cultured N gonorrhoea were subtyped by serological (serovar) and cultural (auxotype) methods and antibiotic sensitivities measured by minimum inhibitory concentration (MIC).

RESULTS

Four of the patients had severe gonorrhoea-related systemic or extragenital symptoms: disseminated gonococcal infection with oligoarthritis (1 patient), acute pelvic inflammatory disease (1 patient, who was also chlamydia positive) and tender inguinal adenopathy (2 patients). The fifth patient was asymptomatic. N gonorrhoeae was isolated in four of the patients. All four organisms had identical MICs. Three of the organisms were subtyped and found to be the same rare strain (serovar 1A1, auxotype NR).

CONCLUSION

This case cluster provides evidence for strain-related virulence in an uncommon gonococcal subtype.

The sensitivity of 173 Sydney isolates of Neisseria gonorrhoeae to cefpodoxime and other antibiotics used to treat gonorrhea

One hundred and thirty seven consecutive isolates of Neisseria gonorrhoeae and a further 36 selected gonococci with either chromosomal (CMRNG) or plasmid mediated (PPNG) resistance to penicillin, all cultured in Sydney in 1993, were found to be sensitive to cefpodoxime, an oral third generation cephalosporin antibiotic (MIC range < 0.001-0.25 mg/L). All isolates were also sensitive to ceftriaxone and spectinomycin. Six gonococci showed high level resistance to tetracycline (TRNG, MIC = 32 mg/L) and 12 had decreased susceptibility to quinolone antibiotics (MIC range 0.06-0.5 mg/L). The MIC50 and MIC90 for both cefpodoxime and ceftriaxone were highest amongst CMRNG and ceftriaxone was 2 to 4 times as active as cefpodoxime weight for weight. Cefpodoxime may be a valuable additional oral agent for the treatment of gonorrhea in Australia. The sensitivity of gonococci to cefpodoxime can probably be inferred from values obtained for ceftriaxone.

The incidence of gonorrhoea and the antibiotic sensitivity of gonococci in Australia, 1981-1991. The Australian Gonococcal Surveillance Programme

OBJECTIVE

To review and analyse the changing incidence of gonorrhoea and the increasing antibiotic resistance in gonococci in Australia from 1981 to 1991.

DESIGN

Use of data from the sample of gonorrhoea in Australia examined by the Australian Gonococcal Surveillance Programme (AGSP), a continuing long-term multi-centric study of gonococcal disease and gonococcal susceptibility to antibiotics, over the period 1 July, 1981 to 30 June, 1991.

RESULTS

Over 32,000 cases and strains from defined sources were examined in the 10 year study period. The number of cases of gonorrhoea in the sample decline from a peak of 6599 in 1982-1983 to 1121 in the final year under review, a reduction of 83%. Periods when greater than average reductions in incidence occurred in different groups were noted. Ano-rectal gonorrhoea in men decreased sharply in 1985 during an overall decline of 92.5% recorded between 1 July, 1981 to 30 June, 1987. However, the incidence of ano-rectal cases in males rose in subsequent years while gonorrhoea, overall, continued to decrease and at a greater rate after 1985. Antibiotic resistance in gonococci in Australia was manifested both as a progressive increase in the levels of intrinsic resistance to the penicillins and through the appearance and spread of penicillinase-producing N gonorrhoeae (PPNG). At the end of the review period in June, 1991, 8.8% of gonococcal isolates in Australia showed high levels of intrinsic resistance to the penicillins and 13% of strains were PPNG. These separate mechanisms of resistance appeared at different times in different parts of Australia, and their importance also varied throughout the country. Most infections with PPNG were acquired by men overseas whereas most women with PPNG were infected locally. Endemic spread of PPNG was a significant problem in Sydney and Melbourne, but decreased in importance in the later years of the study.

CONCLUSIONS

In the past decade a large reduction in the incidence of gonorrhoea and, by implication, other STDs has occurred in the past decade in Australia. In some groups of patients the decline in incidence is continuing while in others a slight increase has been noted. Resistance to antibiotics of gonococci in Australia was mainly restricted to the penicillins, but through both chromosomal and plasmid-mediated mechanisms. This resistance was seen particularly in Sydney and Melbourne where endemic cycles of transmission of PPNG were established, and in infected travellers from S-E Asia in other centres. Valid and comparable, and regionally relevant data are a continuing requirement for assessing and modifying antibiotic treatment regimens for gonococcal disease.

A case of gonococcal mastitis in a male

A case of a 42 year old homosexual man with mastitis of the left breast due to Neisseria gonorrhoeae is presented on account of its extreme rarity. It was probably acquired as a result of direct oral-nipple contact.